The polymer electrolytes composed of the blend of poly(vinylidene fIuoride-co-hexafluoropropylene) [P(VdF-co-HFP)], and poly(methyl methacrylate-co-lithium methacrylate) [P(MMMA-co-LiMA)] ionomer, and the mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC), and LiPF6 salts were prepared. The introduction of the ionomer into P(VdF-co-HFP) was found to enhance the compatibility of the polymer matrix with the liquid electrolyte. This increase of compatibility could lead to the increase in the uptake amount of the liquid electrolyte into the porous matrix and the ionic conductivities at ambient and sub-ambient temperature were, thus, enhanced. The charge-discharge efficiency of the carbon/polymer electrolytes/LiCoO2 cell was also significantly improved by introducing the ionomer into the P(VdF-co-HFP) matrix for the polymer electrolyte.